<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- This manual is for FFTW
(version 3.3.10, 10 December 2020).

Copyright (C) 2003 Matteo Frigo.

Copyright (C) 2003 Massachusetts Institute of Technology.

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by the Free Software Foundation. -->
<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Wisdom of Fortran? (FFTW 3.3.10)</title>

<meta name="description" content="Wisdom of Fortran? (FFTW 3.3.10)">
<meta name="keywords" content="Wisdom of Fortran? (FFTW 3.3.10)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html" rel="start" title="Top">
<link href="Concept-Index.html" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Calling-FFTW-from-Legacy-Fortran.html" rel="up" title="Calling FFTW from Legacy Fortran">
<link href="Upgrading-from-FFTW-version-2.html" rel="next" title="Upgrading from FFTW version 2">
<link href="Fortran-Examples.html" rel="prev" title="Fortran Examples">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<span id="Wisdom-of-Fortran_003f"></span><div class="header">
<p>
Previous: <a href="Fortran-Examples.html" accesskey="p" rel="prev">Fortran Examples</a>, Up: <a href="Calling-FFTW-from-Legacy-Fortran.html" accesskey="u" rel="up">Calling FFTW from Legacy Fortran</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Wisdom-of-Fortran_003f-1"></span><h3 class="section">8.5 Wisdom of Fortran?</h3>

<p>In this section, we discuss how one can import/export FFTW wisdom
(saved plans) to/from a Fortran program; we assume that the reader is
already familiar with wisdom, as described in <a href="Words-of-Wisdom_002dSaving-Plans.html">Words of Wisdom-Saving Plans</a>.
</p>
<span id="index-portability-8"></span>
<p>The basic problem is that is difficult to (portably) pass files and
strings between Fortran and C, so we cannot provide a direct Fortran
equivalent to the <code>fftw_export_wisdom_to_file</code>, etcetera,
functions.  Fortran interfaces <em>are</em> provided for the functions
that do not take file/string arguments, however:
<code>dfftw_import_system_wisdom</code>, <code>dfftw_import_wisdom</code>,
<code>dfftw_export_wisdom</code>, and <code>dfftw_forget_wisdom</code>.
<span id="index-dfftw_005fimport_005fsystem_005fwisdom"></span>
<span id="index-dfftw_005fimport_005fwisdom"></span>
<span id="index-dfftw_005fexport_005fwisdom"></span>
<span id="index-dfftw_005fforget_005fwisdom"></span>
</p>

<p>So, for example, to import the system-wide wisdom, you would do:
</p>
<div class="example">
<pre class="example">        integer isuccess
        call dfftw_import_system_wisdom(isuccess)
</pre></div>

<p>As usual, the C return value is turned into a first parameter;
<code>isuccess</code> is non-zero on success and zero on failure (e.g. if
there is no system wisdom installed).
</p>
<p>If you want to import/export wisdom from/to an arbitrary file or
elsewhere, you can employ the generic <code>dfftw_import_wisdom</code> and
<code>dfftw_export_wisdom</code> functions, for which you must supply a
subroutine to read/write one character at a time.  The FFTW package
contains an example file <code>doc/f77_wisdom.f</code> demonstrating how to
implement <code>import_wisdom_from_file</code> and
<code>export_wisdom_to_file</code> subroutines in this way.  (These routines
cannot be compiled into the FFTW library itself, lest all FFTW-using
programs be required to link with the Fortran I/O library.)
</p>


</body>
</html>
